It is well known that the efficacy of lubricating compositions deteriorates over time as a result of exposure to thermal, oxidative and other environmental stresses. In order to avoid decreased performance, excessive wear and possible component failure of mechanical equipment as a result of using a lubricant beyond its effective life it is necessary to conservatively schedule lubricant change intervals or to resort to frequent sampling and analysis of the lubricant.
In industrial environments oil analysis constitutes an important role in preventive maintenance programs. This analysis, however, typically is conducted off-site and results are not normally available as soon as desirable. Thus, there is a need for a liquid monitoring system that can be conducted continuously on-line.
One approach to a more continuous monitoring of a liquid's quality is to measure the properties of the liquid by an electrochemical impedance technique; and currently there are commercially available sensors for making such measurements. Unfortunately results can be problematic because a viscosity change in the fluid being measured could result in a change in the fluids conductivity.
Presently there are a number of different types of instruments and methods for liquid viscosity measurements, most of which are not suitable for on-line measurements. However, quartz crystal microbalances are commercially available for measuring the viscoelastic properties of a liquid and have been suggested for use in on-line situations.
At present there has yet to be devised a commercially acceptable sensor, or system that is capable of simultaneously monitoring the electrochemical and viscoelastic properties of a lubricant. Thus there remains a need for a method and device, or system, that can simultaneously monitor the electrochemical and viscoelastic properties of a lubricant, or other liquid hydrocarbons.
An object of the present invention is to provide a single sensor that can simultaneously measure the electrochemical impedance and viscosity of a lubricant.
Another object of the invention is to provide a single sensor that can discriminate between viscosity information and electrochemical measurements.
Yet another object of the invention is to provide a simple data analysis method to separate the viscoelastic and electrochemical measurements.
Other objects and advantages of the invention will become apparent upon a reading of the description which follows.